The present invention has an object to provide a device for avoiding multiple shocks, against a target member, of a weighty mass falling thereon along a rectilinear trajectory. These multiple shocks result because of the bounces of the mass after the first impact.
More precisely, the invention concerns a device for avoiding multiple shocks of a mass associated with guide means and falling along a rectilinear direction towards a target member couple with the earth, as a result of the bounces of the mass after the first impact.
This device may be used, for example, in combination with an apparatus for generating in the earth longitudinal acoustic waves. Such an apparatus is described in French Pat. No. 2,398,316. It essentially comprises a target member secured at a first end of a guide tube forming the guide means and arranged so as to come in contact with the earth when the tube is in a substantially vertical position. A mass is provided adapted to impinge on the target member, and its fall is guided by the guide tube and means for moving said mass to an upper position at the second end of the tube and to maintain it intermittently in said position until the selected triggering times.
This apparatus has the disadvantage of not being provided with means for controlling the free motion of the mass after the first impact, the latter usually effecting multiple bounces of decreasing amplitude, thereby generating multiple shocks on the target member. Multiple secondary impulses are generated in addition to the primary impulse resulting from the first impact, with a disturbing effect on the recordings and result in a lower resolution power of the seismic apparatus.